Thursday, 3 March 2016

False Bay wildlife - Cape fur seals

Cape fur seal.

Cape Fur seals,
also known as the South African seals, are named after than pelt which is
thicker than most seals and have a thin layer of hair. These seals are a slightly
larger subspecies than Australian fur seals. Being sexually dimorphism, males and
females differ in size, with bulls growing up to 2.5 m while cows can grow up to
1.6 m.

Males' coats range
in shades of brown, from caramel through to dark chocolate while females are
often more a silver-grey tone. New born pups are black in colour, moulting
between the ages of 3 to 5 months and then turn into an olive grey colour. After
a year of age, pups turn a silver-grey shade.

These seals are
referred to as eared seals because of their endearing, rolled up ears. Their
whiskers help to detect potential prey in dark and murky water while their
limbs act as flippers and help to scratch itches.

They
have bodies that are streamlined in shape making them great swimmers. Although
better suited for the aquatic life, these mammals are somewhat nimble on land
and are even able climb rocks.

Habitat

Cape fur seals are
found along the southern and south-western coast of Africa, stretching from
Namibia through to South Africa. In the country of South Africa, these seals
are found from the Cape of Good Hope, through to the Black Rocks located near
Port Elizabeth, in the Eastern Cape.

In False Bay,
there is small island set off the northern beaches of the bay about 5.7 km (3.5
miles) out to sea. Seal Island was given its’ name due to the great number of
seals that inhabit the island. Currently there are 64 000 Cape fur seals that
call the island their home and that number is increasing.

Mother Cape fur seal and pup.

Behaviour

They are social,
active and inquisitive animals when in the water, however become less relaxed
and more anxious when on land. These friendly dogs of the sea have a range of
vocalisations for communicating with one another.

Seals have 2
sleeping patterns, one on land and one designed for sleeping in water. They
sleep on land just like any other land mammal but do open their eyes occasionally
to check the coast is clear for predators. In the ocean, they are able to rest
different parts of their brain, at different times, enabling them to stay afloat
by paddling one fore flipper at a time. Just like on land, in water they open
one eye briefly to check for potential predators.

In the waters
surrounding Seal Island, Cape fur seals have been observed using several tactics
to avoid the capture of predators, namely the Great White shark. These seals
swim in large groups harassing sharks and are seen darting about in different
directions in order to confuse predators. They use their nature agility in the water to
stay out of reach and swim near dorsal fins of sharks as a way to keep away
from their jaws.

Diet

Cape fur seals eat
seafood and a varied mix of it, from fish and rays through to octopus and
squid. These seals usually prefer to hunt along, however, occasionally will
hunt in packs of up to 15 individual seals. A Cape fur seal is able to dive to
depths of up to 200 metres and can hold their breath for an impressive 7.5
minutes.

Cape fur pup.

Reproduction

During late
October, adult males flop ashore onto Seal Island and are shortly followed by females. Males spend 6 weeks on land protecting their harem, often made of
up to 66 females, living off their fat reserves stored in their blubber.

Females give birth
in late November through to early December, and between 6 to 10 days can be impregnated
again by the dominant male. A standard gestation period is 8 months but females
only give birth after 12 months, this is due to a process called ‘delayed
implantation.’ After a male and female copulate, the fertilized egg only begins
to grow after 4 months within the womb of the female.

During the first 3
months after the birth of the pup, the mother seal follows a roster of 3 days
on land and 4 days at sea to hunt. Upon returning back to the colony, she calls
out for her pup and the pup answers back with its very own call. When the
mother reaches her pup, she sniffs to pick up on the distinctively unique scent
of her pup, and then proceeds to feed her baby seal.

Did you know?

Seals live on average for 25 - 30 years, with females
usually live longer than males.